Electrochemical cyanation of selected aromatic compounds



United States Patent 3,431,184 ELECTROCHEMICAL CYANATION 0F SELECTEDAROMATIC COMPOUNDS Sam Andreades, Wilmington, DeL, assignor to E. I. du

Pont de Ncmours and Company, Wilmington, DeL, a

corporation of Delaware No Drawing. Filed Feb. 16, 1966, Ser. No.527,752 US. Cl. 294-59 12 Claims Int. Cl. Btlllr 1/00; (107a 121/60,]2]/50 ABSTRACT OF THE DISCLOSURE Mono and dicyano carbocylic aromaticand nitrogen heterocyclic aromatic compounds are produced by passing adirect current of electricity through a solvent or mixture of solventscontaining a cyanide-containing compound and a carbocyclic aromatic ornitrogen heterocyclic compound. The aromatic reactant contains 1-4 ringsand bears not more than four substituents. The process is conducted at atemperature of about -50 to +100 C. at an anode potential (versus aSaturated Calomel Electrode) of the order of +0.5 to +3.5 volts using anessentially inert anode.

Description of the invention This invention relates to a matic nitriles.

More specifically, this invention relates to electrochemical cyanations,e.g., the introduction of cyanide functionality into carbocyclic andheterocyclic compounds to produce aromatic nitriles.

The process of this invention comprises passing a direct current ofelectricity through a medium containing an aromatic compound and acyanide-containing compound to introduce nitrile functionality into thearomatic reactant. Depending upon the aromatic reactant, the productproduced contains one or more nitrile groups.

The process comprises electrolyzing at an anode potential below that atwhich substantial attack of the solvent occurs, an aromatic compoundcomposed of carbocyclic or nitrogen heterocyclic rings having anaromatic system of double bonds. Carbocyclic and heterocyclic aro maticcompounds which can be electrochemically cyanated by the process of thisinvention contain 14 aromatic rings bearing not more than foursubstituents wherein the substituents are selected from the group alkylcontaining up to 12 carbon atoms, F-, NC-, Cl-, Br, O N-, alkyl-O-containing up to 12 carbon atoms, phenyl, phenoxy, or alkyl-S containingup to 12 carbon atoms. Compounds containing not more than three aromaticrings are preferred.

Aromatic compounds used include substituted and unsubstituted benzenes,naphthalenes, anthracenes, phenanthrenes, Chrysenes, pyrenes, pyridines,and quinolines. The naphthalene, pyridine and quinoline reactants haveat least one unsubstituted alpha position and anthracene isunsubstituted in the 9 position. Chrysenes should have position 2unsubstituted and preferably one or more of positions 4, 5, 6, 10, 11and 12 should also be unsubstituted. In the pyrenes at least two ofpositions 3, 5, 8,

process for preparing aroand 10 are unsubstituted. The numbering usedfor chrysenes and pyrenes conforms to the following formulas:

It is preferred that not more than one NC, Br, or O N group be presenton one ring of aromatic compound and is is further desirable that atleast one alkyl- O- or al'kyl-S- substituent be present when thearomatic compound has NC or Br-- substituents.

Compounds suitable as the aromatic reactant include: toluene, o-xylene,m-xylene, p-Xylene, mesitylene, 1,2,3,5- tetramethylbenzene,dodecylbenzene, n-hexylbenzene, cumene, 4-n-hexyltoluene, chlorobenzene,2'cyanoaniso1e, methyl-4-butoxybenzene, 4-chlorotoluene,4-chloroethylbenzene, 1,3,5-trimethoxybenzene, butyl hydroquinonedimethyl ether, butyl resorcinol dimethyl ether,1,2-dimethyl-4,5-dimethoxybenzene, fluorobenzene, bromobenzene,4-bromotoluene, 4-nitrotoluene, 4-nitroanisole, dodecyl phenyl ether,dodecyl phenyl sulfide, methyl phenyl sulfide, n-heXyl phenyl sulfide,4,4-dimethoxydiphenyl ether, 4,4-dimethoxydiphenyl,4-phenoxybenzonitrile, dibutylcatechol dimethyl ether, dibutylanisole,4-bromodiphenyl ether, 4-chlorodiphenyl, 4-nitrodiphenyl ether,a-methoxy naphthalene, ,B-methoxynaphthalene, 2,5-dimethoxynaphthalene,1-dodecylnaphthalene, 1,4,5-trimethoxynaphthalene, 1methoXy-4-chloronaphthalene, 1,5 dimethyl-4- 35 methoxynaphthalene,l-naphthonitrile, dodecyl l-naphthyl sulfide, dodecyl l-naphthyl ether,1,4-dimethylnaphthalene,

2,S-dimethylnaphthalene, wphenylnaphthalene, l-chloroanthracene,1-chloro-4-methoxyanthracene, 1-methoXy-4- 4O methylanthracene,l-nitroanthracene, l-cyanoanthracene,

l-dodecylanthracene, dodecyl anthryl ether, 1,4-dimethoxyanthracene,2,6-dimethoxyanthracene, 1,4,5-trimethoxyanthracene, 1,4diethylanthracene, 1 phenoxyanthracene, 1,2,4,S-tetramethylanthracene,l-chlorophenanthrene, l-cyanophenanthrene, l-nitrophenanthrene,l-bromophenanthrene, l-methylphenanthrene, 1,4-dimethylphenanthrene,1,S-dimethylphenanthrene, 1,4,5,8-tetramethylphenanthrene,1,4,8-trimethylphenanthrene, l-chlorochrysene, 1,4-dimethylchrysene,l-methylchrysene, 1- methoxychrysene, l-heptylchrysene, 1- octachrysene,1- methylthiochrysene, 1-dodecylthiochrysene, l-dodecyloxychrysene,1-chloropyrene, l-methylpyrene, l-hexylpyrene, l-methoxypyrene,4-chloropyrene, 3,4 lutidine, 2,4-lutidine, 4-phenylpyridine,4-methoxypyridine, 2-ethoxypyri- 55 dine, 2-dodecylpyridine,2-methylthiopyridine, 2-hexylthiopyridine, Z-methylpyridine,S-methylpyridine, 3 -methoxypyridine, 3-ethoxypyridine,3-propoxypyridine, 3,4- dimethoxypyridine, 4-dodecyloxypyridine,4-dodecylthiopyridine, lepidine, 4-hexylquinoline, B-methylquinoline, 4-phenoxyquinoline, 4-phenylquinoline, 4 -methoxyquinoline,4-hexylthioquinoline.

Many other aromatic compounds, not listed above, can be used as thearomatic reactant.

Cyanide-containing compounds useful in electrochemical cyanations as thesource of cyanide ion and as the electrolyte comprise hydrogen cyanide,and salts, and mixtures thereof, and mixtures containing any cyanidesalt soluble in the reaction medium. Examples of cyanidecontaining saltsare: the alkali-metal cyanides, mercurous cyanide, cuprous cyanide andquaternary salts such as R NAg(CN) and (R) XCN wherein X is nitrogen,phosphorous or arsenic and R is a group selected from phenyl, .aralkylcontaining up to 18 carbon atoms and alkyl containing up to 18 carbonatoms. Examples of the latter class of cyanide-containing compounds are:tetramethylammonium cyanide, octadecyltrimethylammonium cyanide,dioctadecyldimethylammonium cyanide, benzyltrimethylammonium cyanide,tetramethylphosphonium cyanide and tetr-aphenylarsonium cyanide.Mercurous cyanide, R NAg(CN) and cuprous cyanide are generally used incatalytic quantities with other cyanide-containing compounds; when used,they sometimes have a catalytic effect on the electrochemical cyanation.The quatern ry ammonium, phosphonium and arsonium salts are readilyprepared by the metathetical reaction of the corresponding quaternaryhalide and an alkali-metal cy nide in an organic solvent. Alkali-metalchloride precipitates from the reaction mixtures. The quaternary cyanideis soluble in the organic medium. The quaternary cyanides are isolatedby evaporation and crystallization techniques.

Electrochemical cyanations can be conducted in any of the various typesof electrolysis cells commonly used for electrolytic reactions (A.Weissberger, Tecniques of Organic Chemistry, vol. II, IntersciencePublishers, Inc., New York, 1956, 385). These cells are modifications ofthe simple electrolysis cells comprising two electrodes, one being acathode and the other an anode, which are suspended in an electrolyte,medium. Some electrolysis cells are divided, that is, the anode and thecathode are suspended in separate media, which is connected by means ofa semi-permeable membrane. Divided cells can be used where the aromaticreactant or solvent is susceptible to reductionfor example,nitrobenzene. In general, most electrochemical cyanations can beconducted in undivided electrolysis cells. Various electrical conductorscan be used as the material of construction for the cathodes and anodesfor electrochemical cyanation. The efficiency of the electrochemicalcyanation is dependent upon the composition of the electrodes and thearomatic reactant, as well as other factors.

In general, inert electrodes with oxygen overpotentials between nickeland gold, including carbon, are used as the anode in the process of thisinvention. Copper, tin, zinc, and silver may be used in certain cases.However, they tend to dissolve during electrolysis to form cyanidecomplexes which makes their use inconvenient. Platinum, palladium,rhodium, carbon, lead, lead dioxide, and nickel are examples of usefulanode materials. Preferably the materials used as cathodes have ahydrogen over-potential less than that of mercury and the cathodematerial is inert to the electrolyte. However, the restriction that thecathode be inert can be obviated to some extent by use of a divided cellwhich permits an electrolyte to be employed in the cathode compartmentdifferent from that in the anode compartment. Materials especiallyuseful as the cathode include copper, nickel, lead, iron, zinc,platinum, rhodium and palladium.

The configuration of the electrodes can be varied. For example, exceptfor mercury, bars, strips and gauzes composed of the above materials canbe used. In the Examples given below, an undivided electrolysis cellconsisting of a stationary cylindrical platinum gauze cathode and arotating cylindrical platinum gauze anode was used. These electrodeswere constructed of concentric -mesh platinum gauze cylinders. Theoperating electrode had a surface area of from 150 to 200 squarecentimeters (determined by a modified B.E.T. method). The anode wasrotated at about to 300 revolutions per minute. The

cell capacity was about 400 milliliters. The anode potential wasmonitored using a Saturated Calomel Electrode (S.C.E.). This cell wasconstructed in such a manner that a relatively large ratio of electrodesurface area to the volume of electrolyte medium was obtained. Relativemotion between the electrolyte medium and the electrodes was produced byrotating the anode. Relative motion between electrodes and medium can beobtained by circulation of the medium through a cell equipped withstationary electrodes.

Solvents used as the cell medium comprised acetonitrile, methanol, N,N-dimethylformamide, N,N-dimethylacetamide, nitrornethane, acetone andmixtures of these solvents. Aqueous mixtures of these solvents can beused. Acetonitrile, which has a relatively large negative and positivedischarge potential and possesses good solubilizing characteristics foraromatic reactants and cyanidecontaining compounds is a preferredsolvent. Methanol is also a preferred solvent.

In general, any electrolyte which is soluble in the medium and whichcontains an anion which is not easily oxidized can be used inconjunction with the cyanidecontaining compounds. Examples ofco-electrolytes which can be used are: tetraethylammonium perchlorate,tetrapropylammonium p-toluenesulfonate and tetrabutylammoniumperchlorate. Other substances such as a small amount of sulfuric acid insome cases improve the conductivity of the electrolysis medium andpromote electrochemical cyanation. Preparation of these electrolytes hasbeen described, R. Shriner, R. Fuson and D. Curtin, SystematicIdentification of Organic Compounds, 5th edition, J. Wiley and Sons, NewYork, 1964.

The electrochemical cyanation process of this invention is conducted ata temperature of about 50 to C. depending upon the medium. Theelectrolyte should be in the liquid state. Pressure under which theelectrochemical cyanation is conducted is not critical. Reactionpressures of subatmospheric and superatmospheric can be used. Ingeneral, the process is conducted at, or near, atmospheric pressure,i.e., at a pressure in the range of 0.5-10 atmospheres.

The amount of current passed through the electrolysis cell should equalat least one Faraday per mole of aromatic reactant in order to obtaingood yields. A large excess of current (2-3 Faradays per mole ofaromatic compound) is desirable to improve the yield of nitrile product.Some product will be formed at lower levels of current consumption, thatis, less than one Faraday per mole of aromatic reactant.

The anode potentials cited in the examples below were measured withrespect to a Saturated Calomel Electrode (S.C.E.) and were usually ofthe order of +0.5 to +3.5 volts. Cyanide ion is oxidized at thesepotentials. Anode potentials higher than +3.5 volts may sometimes beused. However, potentials strong enough to cause substantial oxidationof the solvent are preferably avoided. The potential drop between anodeand cathode in general will be considerably larger than 3.5 volts.

The products obtained by electrochemical cyanations fall into threeclasses, (a) wherein the original substituents on the aromatic compoundare unchanged except for the introduction of one or more cyano groups,(1)) in which one or more of the original substituents on the aromaticcompound has been replaced by cyano groups and (c) wherein originalsubstituents on the aromatic compound are replaced by cyano groups andadditional cyano groups are added. Alkyl substituted aromatic compounds,anisole, m-dialkoxybenzenes and anthracene yield products falling intothe first class and oand p-dialkoxybenzenes yield products fallingwithin the second class. Electrochemical cyanation of p-xylene anisole,m-dialkoxybenzene and anthracene give 1,4-dimethyl-2-cyanobenzene,p-methoxybenzonitrile, 2,4-dialkoxybenzonitrile and9,10-dieyanoanthracene, respectively; 0- and p-dialkoxybenzenes give 2-and 4-alkoxybenzonitriles, respectively.

The following examples further illustrate the invention. The number ofFaradays of electricity passed through the cell is determined bycontinuously recording and integrating the number of amperes ofelectricity passed through the cell as a function of time. The number ofFaradays is calculated from the number of ampere-hours consumed.Voltages at the anode are expressed with reference to a SaturatedCalomel Electrode. Temperatures are expressed in degrees centigrade.

EXAMPLE I Electrochemical cyanation of p-xylene p-Xylene (20.0 g.), g.of potassium cyanide and 110 ml. of methanol were electrolyzed under anitrogen atmosphere using an anode potential of 3.5 v. for 3 hours and3.0 v. for 18 hours. The cell voltage drop was varied from 4.0-5.5 v. inthe course of the reaction. Total current consumed was 1.3 Faraday.After electrolysis, the methanol was evaporated from the dark orangemixture. The residue was treated with 100 ml. of water and ex tractedfour times with 50-ml. portions of ether. The combined ether layers weredried and distilled. After removal of the ether, distillation of theextract gave: fraction 1, B.P. 67-69 (1.5 mm., 7.6 g.); fraction 2, B.P.70l13 (1.5 m., 2.0 g.); fraction 3, B.P. 1l3-l40 (1.5 mm, 1.3 g.);fraction 4, B.P. 140-l82 (1.5 mm., 1.3 g.); fraction 5, B.P. 183 (1.5mm., 0.5 g.). Fractions 1 and 2 were colorless, 3 and 4 were yellow and5 was orange. Slight decoposition occurred during the distillation of 4and 5. Fractions 25 showed strong nitrile infrared absorption and werelargely 2,5-dimethylbenzonitrile, while fraction 1 showed only weaknitrile absorption. Fraction 1 was almost pure p-(methoxymethyl)toluene.

The nitrile products were purified by liquid chromatography on neutralalumina (activity grade 1) in benzene. 2,5-dimethylbenzonitrile and thehydrolysis product of the nitrile, 2,5-dimethylbenzamide, were obtained.

EXAMPLE II Electrochemical cyanation of p-xylene The procedure ofExample I was repeated using 10.0 g. of potassium cyanide, 110 ml. ofmethanol, 0.1 g. of cuprous cyanide and 20.0 g. of p-xylene.Electrolysis was carried out at 35 C. at a potential of +3.5 v. and

a total current consumption of 1.11 Faraday over a 19- r hour period.Workup in the usual manner gave 2.2 g. B.P. -60" (3 mm.) and a remainingred residue of 22 g. The distillate was a mixture of methylp-methylbenzyl ether and p-toluic aldehyde.

The residue was eluted from a column of 300 g. of neutral alumina(activity grade 1) with benzene to obtain fraction 2 (0.674 g.) andfraction 3 (10.24 g.). Elution with ether gave fraction 4 as 2.18 g.Fractions 2-4 showed strong nitrile absorption at 4.5 1. By vapor phasechromatographic analysis, fraction 2 was 31% p-(methoxymethyl)tolueneand 34% 2,5-dimethylbenzonitrile. Fraction 4 was 38% of the methyl etherand 18% of the nitrile. Fraction 3, which contained about 50% nitrileand 50% of the ether, was rechromatographed on 300 g. of alumina toyield 3.5 g. of pure 2,5-dimethylbenzonitrile, established by comparisonof its infrared spectrum and its gas chromatographic retention time withthose of an authentic sample. An addition 5.1 g. of the nitrile wasobtained by further treatment of fraction 3.

A similar electrolysis was carried out using tetraethylammonium cyanide(preparation described below) instead of potassium cyanide. Cuprouscyanide was added. Cyanation again occurred but in lower yield. Inaddition, it was observed that more oxidation of a Xylene methyl groupto an aldehyde occurred when the tetraethylammonium salt was used inplace of the potassium salt.

EXAMPLE III Electrochemical cyanation of biphenyl A solution of 10.0 g.(0.065 mole) of biphenyl, 10.0 g. (0.153 mole) of potassium cyanide inml. of methanol was electrolyzed using an anode potential of +1.75 v.The current dropped from 2.5 amp to 0.3 amp in two hours. Total currentconsumed was 0.5 Faraday in 23 hours. The mixture slowly turned orangeas electrolysis proceeded and at the end of the electrolysis the currentlevel has dropped to 0.03 amp. The mixture was Worked up in the usualmanner and the final distillation gave 2.0g. of biphenyl and 2.8 g. ofp-phenylbenzonitrile, B.P. 139 (0.5 mm.) with a residue of 2.1 g. Thedistillate was purified by chromatography on alumina. using benzene asthe eluent. p-Phenvlbenzonitrile eluted as the only early product andcrystallized. The chromatographic cuts were combined and recrystallizedfrom hexane to give pure product, M.P. 83-84.

Analysis.Calcd for C H N: C, 87.12; H, 5.06; N, 7.82; M.W., 179.21.Found: C, 86.97; H, 4.96; N, 7.75.

The n.m.r. spectrum showed aromatic absorption at 2.6 which appeared toinclude an A-B pattern derived from the two kinds of protons on the ringbearing the nitrile group, viz., the protons adjacent to the CN groupand those adjacent to the C 11 group.

EXAMPLE IV Electrochemical cyanation of anthracene (3N EtrNCN CHsCNElectr. 0N

Part A A solution of 50 g. of sodium cyanide: in 1.5 liters of methanolwas added to a stirred solution of 100 g. of anhydroustetraethylammonium chloride in 200 ml. of methanol. The entire operationwas conducted under nitrogen. The reaction mixture was filtered and thefiltrate was evaporated to dryness under reduced pressure. The residuewas extracted with 1 liter of dry acetonitrile. The extract Was thenevaporated under reduced pressure. Crystals of Et NCN formed during theconcentration. When about 200 ml. of solution remained, 47 g. of Et NCNwas collected on a filter and was washed with acetonitrile.

Anaiysis.Calcd for C H N C, 69.17; H, 12.90; N, 17.93. Found: C, 69.82;H, 12.96; N, 17.77.

On dilution with tetrahydrofuran, the filtrate yielded an additional 28g. of Et NCN, which was recrystallized from acetonitrile before use.

Part B A solution containing 0.53 g. (3 mmoles) of anthracene and 6.0 g.(38.5 mmoles) of tetraethylammonium cyanide in 300 ml. of acetonitrileand 100 ml. of ether was electrolyzed for 0.6 hour at an anode potentialof 2.0 v. Total current passed was 0.027 Faraday. After completion ofthe electrolysis, half of the acetonitrile and ether was evaporated, themixture was diluted with water and filtered to give 0.373 g. of crude9,10-dicyanoanthracene. This solid was dissolved in boiling benzene andthe solution filtered to remove some dark amorphous impurities. Oncooling, the solution deposited 73 mg. of greenish yellow needles of9,10-dicyanoanthracene, M.P. 340341 (dec., sealed capillary, lit. M.P.,334). The infrared spectrum was identical to that of an authenticsample.

7 Analysis.-Calcd for C H N C, 84.2; H, 3.5; N, 12.3; M.W., 228. Found:C, 84.3; H, 3.88; N, 11.35; M.W., 228 (mass spec).

EXAMPLE V Electrochemical cyanation of diphenyl ether Electr.

A solution of 10.0 g. of potassium cyanide, 20.0 g. of diphenyl ether(0.117 mole), 0.1 g. of cuprous cyanide and 110 ml. of methanol waselectrolyzed at an anode potential of +0.5 v. for 1.5 hours, +1.75 v.for 2 hours, +2.5 v. for 2 hours, and +3.0 v. for 21 hours for a totalcurrent consumption of 0.4 Faraday. The mixture was worked up in theusual manner. Final distillation gave fraction 2, BF. 8990 (1.5 mm.,10.3 g.) which was essentially pure diphenyl ether, fraction 3, Bl.90-145 (1.5 mm., 0.7 g.) which was a mixture of a nitrile and a materialabsorbing at 6.0 1. in the infrared spectrum and fraction 4, 13.1.145-l67 (1.8 mm., 0.9 g.) which showed strong 6.0 1 absorption. Aresidue of 4.2 g. black liquid was obtained. The residue and fraction 4were combined and chromatographed on 150 g. of alumina. Elution withbenzene gave 2.8 g. (0.0144 mole) of analytically pure p-cyanophenylphenyl ether. The n.m.r. spectrum showed only a strong symmetricalaromatic multiplet centered at 2.41. The yield was 27.3 percent at 45percent conversion.

Analysis.-Calcd for C H NO: C, 79.99; H, 4.65; N, 7.17; M.W., 195.22.Found: C, 79.47; H, 4.74; N, 6.73; C, 80.05; H, 4.72; N, 6.91; M.W., 179(cryoscopic in benzene).

EXAMPLE VI Electrochemical cyanation of pyridine ON Q Q H2804 Electr.

A solution consisting of 10.0 g. of anhydrous hydrogen cyanide and 100ml. of pyridine allowed no current flow at an applied potential of 5.0v. (anode potential +3.0 c.). Therefore, 0.6 g. of concentrated sulfuricacid was added. At this point, a current of 0.6 tained at an anodepotential of +3.5 v. but the current again dropped as 17 ml. ofcyclopentene were added, and levelled ofi at 0.1 amp. In 5.5 hours,0.065 Faraday was consumed. The mixture was worked up by evaporation ofthe pyridine, dilution of the concentrate with water and extraction ofthe aqueous solution thus obtained with several portions of ether. Thecombined ether extracts were dried over anhydrous sodium sulfate anddistilled to remove starting material to a 13.1. of 48.5" C. at 76 mm.,leaving a residue of 0.5 g. This residue was largely 2-cyanopyridine asshown by IR comparison with an authentic sample. Current yield, 15%.

EXAMPLE VII Electrolytic cyanation of anisole CHsCN Electr.

level was about 0.6 amp. giving a total current consump- 7 amp wasobtion of 0.313 Faraday. Approximately of the acetonitrile was removedunder vacuum on a rotary evaporator and the remaining crude liquid wasdiluted with 100 ml. of water. The aqueous mixture was then extractedfive times with SO-ml. portions of ether. The combined ether layers weredried and distilled. After removal of the ether, a fraction B.P. 86 (0.8mm., 0.3 g.) showed a strong doublet nitrile band in the infraredspectrum. This fraction was identified as anisonitrile by comparison ofits infrared spectrum with an authentic sample. Total yield was 5%.

EXAMPLE VIII Electrochemical cyanation of p-dirnethoxybenzene EtaNCNCHaO--OCH: omoQ-orv ornoN Electr.

A solution of 30.0 g. (0.192 mole) of tetraethylammonium cyanide and10.0 g. (0.0725 mole) of p-dimethoxybenzene in 375 ml. of anhydrousacetonitrile was electrolyzed at an anode potential of +2.0 v. vs.Saturated Calomel Electrode (S.C.E.) for 15 hours. The current decreasedslowly from 1.0 amp to 0.5 amp. A total of 0.5 Faraday was passed. Themixture was worked up in the usual manner which included evaporation ofmost of the acetonitrile, addition of water, repeated extraction of theaqueous layer with ether, aqueous washing and drying of the ether layer,and evaporation of the ether. The remaining 9.5 g. of crude liquidproduct was shown to be 47% anisonitrile and 53% dimethoxybenzene by gaschromatographic analysis. The product contained at least of the abovemixture. The anisonitrile was isolated by preparative gas chromatographyand shown to be identical with an authentic sample by its infraredspectrum. The total conversion was 47% and the yield was 95 In anotherexperiment, electrolysis was carried out until 0.02 Faraday was passed.Analysis of the product indicated a current efficiency of 30%.

When the preparation was conducted in acetonitrile containing 5% water,0.73 Faraday was passed, and, in addition to the anisonitrile, 1 g. ofp-methoxybenzamide was isolated and recrystallized from CH CN; M.P.153-5 (lit., from H O, 163).

Analysis.-Calcd for C H O N: C, 63.51; H, 5.99; N, 9.26. Found: C,63.01; H, 5.82; N, 9.41.

EXAMPLE IX Electrolysis of tetraethylammonium cyanide in the presence ofp-dimethoxybenzene at a low anode potential EMNCN CH30- OCH3 CH30 C NCHaCN Electr.

The previous electrolysis in the presence of p-dimethoxybenzene wasrepeated using an anode potential of +0.9 v., which is suflicient tooxidize cyanide ion in acetonitrile solution but is below the half-waveoxidation potential of p-dimethoxybenzene. Under these conditions, 30hours was required to pass 0.03 Faraday. At the end of this time, thesolution contained 3% anisonitrile and 97% p-dimethoxybenzene. Theresults appear to indicate a current efficiency of 100% at lowconversions.

EXAMPLE X Electrochemical cyanation of veratrole CHsCN 0 CH3 0 CH3Electr. CN 0 CH3 A solution of 10.0 g. (0.072 mole) of veratrole and30.0 g. (0.192 mole) of tetraethylammonium cyanide in 375 ml. ofacetonitrile was electrolyzed with an anode potential of +2.0 v. until0.41 Faraday was consumed. After working up in the manner describedabove, 10.88 g.

of liquid remained which was approximately 78% veratrole and 18%o-methoxybenzonitrile by gas chromatographic analysis. Distillation ofthe liquid gave a fraction B.P. 69-93 (0.6 mm.), 1.7 g. which was 87%veratrole and 13% o-methoxybenzonitrile and a fraction B.P. 93- 110"(0.6 mm), 1.2 g. which was 68% o-methoxybenzonitrile. The nitrile,isolated by preparative gas chromatography from these fractions, wasshown to be identical with an authentic sample by its infrared spectrum.The product was obtained in 20% conversion (94% yield), while thecurrent efficiency was The process of this inVentiOn is useful for themanufacture of a variety of nitrile-containin g compounds. Thesenitrile-containing compounds are useful as intermediates for theproduction of dyes, polymers, and pharmaceuticals. For example,p-methoxybenzonitrile can be converted into esters which are used asodorants and o-methoxybenzonitrile can be converted into salicylateswhich are useful as anti-oxidants.

The foregoing detailed description has been given for clearness ofunderstanding only and no unnecessary limitations are to be understoodtherefrom. The invention is not limited to the exact details shown anddescribed, since obvious modifications will occur to those skilled inthe art.

The embodiments of the invention in which an exclusive property orprivilege is claimed are defined as follows:

1. Process for electrochemical cyanation of aromatic compounds toproduce aromatic nitriles and aromatic dinitriles comprising passing adirect current of electricity at an anode potential of between 0.5 to3.5 volts through a solution containing an aromatic compound and acyanide-containing compound, wherein said aromatic compound is selectedfrom the group consisting of unsubstituted and substituted benzenes,naphthalenes, anthracenes, phenanthrenes, chrysenes, pyrenes, pyridinesand quinolines wherein the substituents are selected from the groupalkyl containing up to 12 carbon atoms, F-, Cl-, Br-, CN, O N, alkyl-Ocontaining up to 12 carbon atoms, phenyl, phenoxy or alkyl-S- containingup to 12 carbon atoms; with the provisos that the substituted aromaticcompounds have no more than four substituents; That when the aromaticcompound is a naphthalene, a pyridine and a quinoline at least one alphaposition is unsubstituted, when the aromatic compound is anthracene the9 position is unsubstituted, when the aromatic compound is a chrysenethe 2 position is unsubstituted, and when the aromatic compound is apyrene at least two of the positions 3, 5, 8 and 10 are unsubstituted;wherein said cyanide-containing compound is selected from the groupconsisting of hydrogen cyanide, alkali-metal cyanides, (R) XCN wherein Ris a group selected from phenyl, aralkyl containing up to 18 carbonatoms and alkyl containing up to 18 carbon atoms and X is selected fromthe group nitrogen, phosphorous and arsenic, cy-

anide mixtures containing cuprous cyanide, mercurous cyanide and (R)NAg(CN) wherein R is a group selected from phenyl, aralkyl containing upto 18 carbon atoms and alkyl containing up to 18 carbon atoms, andmixtures of said cyanide-containing compounds; and wherein theelectrochemical cyanation is conducted in a solvent, in which thearomatic and cyanide-c0ntaining compounds are at least partiallysoluble.

2. Process of claim 1 wherein the aromatic compound contains up to threesubstituents.

3. Process of claim 1 wherein the solvent is identical with the aromaticreactant.

4. Process of claim 1 wherein a non-cyanide-containing salt is added tothe solution, said non-cyanide-containing salt being at least partiallysoluble and containing an anion which is not easily oxidized.

5. Process of claim 1 wherein the solvent is selected from the groupacetonitrile, methanol, N,N-dimethylformamide, N,N-dimethylacetamide,nitromethane, acetone, mixtures of these solvents, and aqueous mixturesof these solvents.

6. Process of claim 4 wherein the non-cyanide-contaim ing compound istetraethylammonium p-toluenesulfonate.

7. Process of claim 4 wherein the non-cyanide-containing compound issulfuric acid.

8. Process of claim 1 wherein the is veratrole.

9. Process of claim 1 wherein the aromatic compound is anthracene.

10. Process of claim 1 wherein is diphenyl ether.

11. Process of claim 1 wherein is diphenyl.

12. Process of claim 7 wherein the aromatic compound is pyridine.

aromatic compound the aromatic compound the aromatic compound ReferencesCited UNITED STATES PATENTS 2/1957 Kamlet 20472 5/1957 Hutchings 204-101OTHER REFERENCES JOHN H. MACK, Primary Examiner. HOWARD M. FLOURNOY,Assistant Examiner.

U.S. Cl. X.R.

